To the Editor:
We describe a 55-year-old woman who presented with epigastric pain radiating to the back, chest discomfort, and fever. Blood tests showed increased level of acute-phase reactants. Computed tomography angiography (CTA) revealed a partially thrombized aneurysm of the superior mesenteric artery and stenosis of the celiac trunk and inferior mesenteric artery. Arteriography confirmed the stenoses. Two angioplasties were successfully performed, leading to prompt resolution of the abdominal pain. She was then treated with acetylsalicylic acid 100 mg/day and clopidogrel 75 mg/day. Nevertheless, her chest pain worsened, she developed a troponin-negative crescendo angina, and was diagnosed with a non-ST-elevation acute coronary syndrome. Cardiac angiography showed normal coronary arteries. Myocardial blood flow was assessed with a combined positron emission tomography-computed tomography (PET/CT) and 13N-ammonia. A stress-rest protocol with dipyridamole was used (Figure 1).
Regional ischemia was detected in the inferoapical and inferior wall, indicating mild hemodynamically significant involvement of the right coronary artery. Left ventricular ejection fraction was normal (73%). Assessment of hypermetabolic foci was performed with a whole-body PET/CT scan and 18F-fluorodeoxyglucose (FDG; Figure 2). Increased tracer uptake (maximum standardized uptake value 3.1) was revealed in the ascending aorta, left subclavian, left common carotid, pulmonary and innominate arteries, and less intense uptake in the thoracic, descending, and abdominal aorta. On the basis of clinical signs, laboratory findings, CTA, and PET/CT scans, the patient was diagnosed with Takayasu arteritis (TA). She was given prednisone 50 mg/day with a tapering schedule and methotrexate 15 mg/week, achieving complete resolution of symptoms. One year later a FDG-PET/CT scan did not reveal any vascular uptake.
TA is a primary large vessel vasculitis of unknown origin that mainly affects the aorta and its branches and is more common in young women. Coronary involvement in TA is not rare, being reported in 7% to 29% of cases, and is associated with high disability and mortality1. Such involvement presents in the form of stenosis, complete obstruction, aneurysm, or coronary steal syndrome. Stenosis or occlusion of the coronary ostium and the proximal segments of the coronary arteries is most frequently detected. Narrowing of the coronary arteries seems to be caused by progression of inflammatory process through the intima, media, and adventitia, leading to fibrosis of the vessel wall2.
Invasive coronary angiography is the clinical gold standard for the diagnosis of coronary artery stenosis and allows immediate treatment with angioplasty. However, it can have complications and may fail to visualize early changes of the coronary arteries.
The use of noninvasive techniques to assess coronary involvement in patients with TA is growing3. FDG-PET has been used in the diagnosis of large vessel vasculitis and, although in part still debated, has a promising role in monitoring disease activity and response to treatment4,5,6. Coronary CTA has been developed into a clinically useful method for visualization of coronary artery stenosis with high negative predictive value, but the evaluation of stenosis is often uncertain7. The PET/CT imaging technique allows a combination of angiography and perfusion imaging in short, quantitative, low-dose radiation protocols and provides information about anatomy and function of arteries8. Perfusion imaging alone could not always separate microvascular disease from epicardial stenoses but PET/CT significantly improved this accuracy, allowing noninvasive detection of coronary artery disease in symptomatic patients as well as the detection and characterization of atherosclerotic plaque9,10.
To our knowledge, this is the first description of coronary artery involvement in TA detected using a PET/CT perfusion scan in a symptomatic patient with normal coronary angiography. This case indicates that cardiac PET/CT perfusion imaging could be a useful noninvasive tool for the early diagnosis and quantitative determination of cardiac perfusion abnormalities in the assessment of active coronary involvement secondary to TA, even earlier than morphologic changes appear on conventional imaging such as CTA and angiography.
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